This invention relates to coated abrasive products that can be made very simply and reproducibly by an easily automated production process.
In a conventional process for the manufacture of coated abrasives, a backing is prepared and then treated with a coat of a maker resin which is then partially cured before a layer of abrasive particles is deposited thereon. The maker coat is then cured and a further binder coat, referred to as a size coat, is applied over the abrasive grains.
The abrasive grain is applied either by gravity coating or by an electrostatic process in which the grains are impelled towards the surface to be coated by electrostatic forces. This is referred to as the UP coating technique.
In such processes the product is conventionally obtained in the form of a roll which is then cut to form discs or strips some of which may be formed into belts. Clearly such a process implies the parallel formation of a significant amount of waste material. Particularly when the grain cost is a significant element in the overall cost of the product, this is a waste that it is desirable to avoid.
In recent years a new form of grain has been developed. This grain has a filamentary particle form with a substantially uniform cross-sectional shape and a length dimension perpendicular to that cross-section that is at least as long as the greatest dimension of the cross-section. One form of such grains is made from a sol-gel alumina that has been shaped into the filamentary particle shape before it is dried and fired to produce a remarkably effective abrasive grain. Such grains are described in U.S. Pat. No. 5,009,676 and coated abrasives made using such particles are described in U.S. Pat. No. 5,103,598.
It has now been found that coated abrasives comprising abrasive particles and particularly filamentary abrasive particles, can be obtained in a highly flexible and efficient way that permits the "customizing" of a coated abrasive to a specific application. Use of the technique will result in minimum wastage of grain and maximum targeted effectiveness of the grain that is used.
Use of the present invention will also avoid the danger that filamentary particles deposited on a substrate may be constrained to adopt a position that departs from the desired orientation before the binder has hardened to the extent that the orientation is fixed.